Transcriptomic Analysis of Hypothalamic Responses in Modern and Legacy Chicken Lines

Broiler chickens have evolved under human selection for rapid growth and high muscle yield. The hypothalamus plays a central role in maintaining energy balance, and it is reasonable to hypothesize that selective pressure on broiler lines may have affected hypothalamic gene expression patterns. To explore this hypothesis, we have compared post-hatch hypothalamic transcriptomes between a modern broiler line, Ross 708, and a legacy line that grows with properties of meat birds from the 1950s. In addition, a portion of the birds was raised under heat stress conditions designed to mimic heat waves. At days 7,21,28 and 42 post hatch, birds were humanely euthanized, and hypothalami isolated and quick frozen in liquid nitrogen. Transcriptomic libraries were prepared using Illumina TruSeq kits, sequenced on an Illumina HiSeq2500 and analyzed using the Tuxedo suite. Relative tissue expression analysis was done using JMP pro11 to identify the genes that are differentially expressed in hypothalamus compared to other tissues. From this analysis, we have identified 894 genes that were enriched in Hypothalamic tissue across all the time points. For specific time points, we have seen enrichment of 884 genes in D7, 897 genes in D21, 972 genes in D28 and 860 genes in D42 Hypothalami samples. From these genes further analysis was done using JMP pro 11 and WEBGIVI tool to identify the genes that were significantly up regulated in hypothalamus compared to mean tissue expression. This resulted in 54 genes in Hypothalamus across all time points and specifically 39 genes in D7, 33 genes in D21, 35 genes in D28, 27 genes in D42 Hypothalami. Pathways, Rate limiting enzymes and the transcription factors that are specifically enriched in this tissue and at the individual time points will be presented.